1. Field of the Invention
The present invention relates to a gas turbine rotor, and more specifically to a sealing structure for rotor discs.
2. Description of the Prior Art
FIG. 4 is a conceptual view showing a general construction of a gas turbine, FIG. 5 is a longitudinal cross sectional view showing one example of the construction of a prior art gas turbine rotor, and FIG. 6 is an enlarged perspective view showing a construction of portion VI of FIG. 5.
As illustrated in FIG. 4, the gas turbine is so constructed that air is compressed at a compressor (1) and fuel is fed into a combustor (2) in order to generate a combustion gas, which is introduced into a turbine portion (3) to rotate a generator (4). A rotor of the turbine portion (3) consists of a plurality of discs (9), as shown in FIG. 5. In order to prevent cooling air (6) in a rotor interior (5) from flowing out into a gas path (7) of the turbine portion as well as to prevent a high temperature gas (8), flowing in the gas path (7) of the turbine portion, from flowing into the rotor interior (5), as shown in FIG. 6, there is provided an annular projection (10) on each surface of the disks adjoining each other so that the annular projections (10) face or oppose each other and surround a rotational axis of the rotor. A groove (11) is provided on or formed in a tip surface of the respective projection (10), and a seal plate or baffle plate (12), which is sectioned into two pieces or four pieces in the circumferential direction, is inserted into the respective groove (11). The baffle plate (12) is pushed to a radial outer side of the groove (11) by a centrifugal force due to rotation so as to effect a seal.
In the prior art rotor disks, it is intended to effect a seal by pressing the baffle plate into engagement with the radial outer side of the groove provided at the projection of the disc by a centrifugal force due to rotation. However, as there is a temperature difference between the discs, a difference in elongation occurs in a radial direction of the groove. There is also a difference in elongation in the radial direction due to a centrifugal force between the discs. As the baffle plate is rigid, it will no longer maintain uniform pressing contact with the outer side of the groove, and minute gaps are created between the groove and the baffle plate. Thus, there is a fear that the cooling air in the rotor interior may flow out into the gas path of the turbine portion, or that the high temperature gas flowing in the gas path of the turbine portion may flow into the interior of the rotor. There is also a concern that the baffle plate may cause a self-induced vibration due to flow leaking from the minute gaps, causing an abrasion loss.